Cavatating tritoon

[hutchie97]

I have a 2004 25 ft sun tracker tritoon with a 150 merc OB. When I am going at faster speeds and I turn the RPMs increase suddenly by a thousand or more and I loose power. I have to back off the throttle and then resume to get it to stop. I have not noticed it when I am going straight. What is the problem and how do I fix it?

 

[5150abf]

Re: Cavatating tritoon

That is a pretty common pontoon thing.

The only cure is to trim down a bit when you start to turn, after you do it a couple times it will become second nature and you wil just do it.

You could lower the motor but that might impact your performance everywhere else, so try trimming down alittle when you turn and I bet it goes away.

 

[tashasdaddy]

Re: Cavatating tritoon

toons are completely different animals from single hull boats. you may just have to slow down going into a turn. even though the are putting bigger motors on toons, they are not designed to be speed boats. when turning a toon, you have 2 or 3 long, narrow hulls you are trying to turn, that want to go straight. thus it takes more pressure to side the stern around, to make the turn. due to the resistance of the hulls, the motor is moving so much water, it blows out, as the water cannot fill in as fast as the prop is push water. so you blow out, which can damage you motor, with the rapid increase in the rpms.

you need to learn what you boat can and can not do. before you blow the motor. nothing worse than flying connecting rods.

 

[hutchie97]

Re: Cavatating tritoon

R u serious? I have to take advice from a golden domer and a gator!
GO BLUE!!

When u say trim down...I am not sure what you mean. I am all the way down already.

Will an anti-cavitation plate help?

Will a slightly damaged prop impact this as well?

thanks

 

[wejsunek]

Re: Cavatating tritoon

let try another prop
andrew

 

[tashasdaddy]

Re: Cavatating tritoon

a damaged prop can effect a lot, also the life of your lower unit. as it is out of balance. thus possible putting extra wear on the bearings.

usually trimming down will help, but if you are all the way in. i suggest lowering the motor height. and that may not help. remember you are trying to push 2 long narrow hulls side ways on the stern. a boat steers just the opposite of a car, car the front wheels turn and the rest follows. a boat wants to go straight, and you slide the stern side was to change direction.

 

[SoulWinner]

Re: Cavatating tritoon

When this happens in a turn it's called "prop slip" over on the pontoon boat sites. My guess is that it is one of two problems; either your prop or the engine placement. First, did the problem exist before the prop was damaged? For starters, ditch the damaged prop. If you boat in water where you are likely to damage another prop, get a pirana ( http://www.piranha.com/ ). Second, where is the motors prop/AC plate in relation to the bottom of the pontoon logs/engine pod. It sounds to me like you either have the wrong prop size or pitch, or your motor isn't low enough in the water. There are several web sites with forums that devoted solely to pontoon boats, and you may find more help for your situation there.

 

[hutchie97]

Re: Cavatating tritoon

soulwinner, can you share some of the websites for pontoons?
Can the motor be too deep on a tritoon?
How do I know what the propper pitch of prop is?

Thanks for everyones great support

 

[SoulWinner]

Re: Cavatating tritoon

http://www.pontoon.net/fusetalk/forum/index.cfm?forumid=3

http://www.pontoonstuff.com/forum/

As far as the depth of the motor, I know they can be too high, I don't know if they can be too deep. However, the prop needs clean water to operate, and they can cavitate in when they encounter turbulent water. This can result from center logs on tri toons, it can happen on pontoons with only two logs in a turn. I believe it can also be related to the pitch of the prop. I own a 20' Crest with Taper-toons with a Merc 115 EFI 4 stroke. It came with a prop with a 10 pitch that let the motor over-rev and would slip in turns. I put one with a 15 pitch on and it made all the difference, my rpms top out at 5700 (don't know the speed with this prop). But I discovered this was a better prop by going to an online prop store and using the Prop Wizard to determine which one I needed.

One thing that a LOT of potoon guys do to solve this exact problem is to add a hydro plane to the motor. If you look on the above listed forums using the search feature you will find a wealth of info regarding the use and limitations of the various hydro-planes on toons.

I hope this helps.